Ultrastructure and histogenesis of the renal tumors of childhood: an overview

Nephroblastoma with Neuroendocrine Differentiation

A nephroblastoma (Wilms' tumor) with morphological, histochemical, immunohistochemical and ultrastructural evidence of neuroendocrine differentiation is described. Whereas areas of neural differentiation and occasional argyrophilic cells in cases of Wilms' tumor have been previously reported, the unique characteristic in this case was the extent of the neuroendocrine differentiation, as shown by a strong Grimelius stain of over 90 % of the blastematous cells. Immunoperoxidase studies employing antibodies to neuron-specific enolase and ultrastructural data were also in favor of the neuroendocrine differentiation and suggested the existence, in addition to the already reported variant of Wilms' tumor with neural differentiation, of a neuroendocrine variant which may be part of the histologic spectrum of this neoplasm.

The developmental programme for genesis of the entire kidney is recapitulated in Wilms tumour

Wilms tumour (WT) is an embryonal tumour that recapitulates kidney development. The normal kidney is formed from two distinct embryological origins: the metanephric mesenchyme (MM) and the ureteric bud (UB). It is generally accepted that WT arises from precursor cells in the MM; however whether UB-equivalent structures participate in tumorigenesis is uncertain. To address the question of the involvement of UB, we assessed 55 Wilms tumours for the molecular features of MM and UB using gene expression profiling, immunohistochemsitry and immunofluorescence. Expression profiling primarily based on the Genitourinary Molecular Anatomy Project data identified molecular signatures of the UB and collecting duct as well as those of the proximal and distal tubules in the triphasic histology group. We performed immunolabeling for fetal kidneys and WTs. We focused on a central epithelial blastema pattern which is the characteristic of triphasic histology characterized by UB-like epithelial structures surrounded by MM and MM-derived epithelial structures, evoking the induction/aggregation phase of the developing kidney. The UB-like epithelial structures and surrounding MM and epithelial structures resembling early glomerular epithelium, proximal and distal tubules showed similar expression patterns to those of the developing kidney. These observations indicate WTs can arise from a precursor cell capable of generating the entire kidney, such as the cells of the intermediate mesoderm from which both the MM and UB are derived. Moreover, this provides an explanation for the variable histological features of mesenchymal to epithelial differentiation seen in WT.

Genomic imbalances pinpoint potential oncogenes and tumor suppressors in Wilms tumors

BACKGROUND

Wilms tumor (WT) has a not completely elucidated pathogenesis. DNA copy number alterations (CNAs) are common in cancer, and often define key pathogenic events. The aim of this work was to investigate CNAs in order to disclose new candidate genes for Wilms tumorigenesis.

RESULTS

Array-CGH of 50 primary WTs without pre-chemotherapy revealed a few recurrent CNAs not previously reported, such as 7q and 20q gains, and 7p loss. Genomic amplifications were exclusively detected in 3 cases of WTs that later relapsed, which also exhibited an increased frequency of gains affecting a 16.2 Mb 1q21.1-q23.2 region, losses at 11p, 11q distal, and 16q, and WT1 deletions. Conversely, aneuploidies of chromosomes 13 and 19 were found only in WTs without further relapse. The 1q21.1-q23.2 gain associated with WT relapse harbours genes such as CHD1L, CRABP2, GJA8, MEX3A and MLLT11 that were found to be over-expressed in WTs. In addition, down-regulation of genes encompassed by focal deletions highlighted new potential tumor suppressors such as CNKSR1, MAN1C1, PAQR7 (1p36), TWIST1, SOSTDC1 (7p14.1-p12.2), BBOX and FIBIN (11p13), and PLCG2 (16q).

CONCLUSION

This study confirmed the presence of CNAs previously related to WT and characterized new CNAs found only in few cases. The later were found in higher frequency in relapsed cases, suggesting that they could be associated with WT progression.

Identification of the transcription factor HOXB4 as a novel target of miR-23a

The transcription factor HOXB4 not only plays a role during nephrogenesis, but displays also oncogenic characteristics in different malignant neoplasms. An in-silico analysis revealed HOXB4 as a new target of microRNA-23a (miR-23a). Nephroblastomas are malignant embryonal renal neoplasms of childhood resembling developing kidney morphologically and genetically. In our study we verified HOXB4 as a target of miR-23a and furthermore examined the expression of HOXB4 and miR-23a in nephroblastomas. We investigated binding of miR-23a to the 3'UTR of HOXB4 by a luciferase assay. Effects on protein levels of HOXB4 were analysed in Western blot experiments. Expression of HOXB4 in nephroblastomas was assessed by quantitative REALtime PCR (qRT PCR) and immunohistochemistry. The luciferase reporter assay showed a statistically significant downregulation of activity by 72,5% demonstrating direct binding of miR-23a to the 3'UTR of HOXB4. In addition, miR-23a reduced the protein expression of HOXB4 statistically significantly by 65.1%. All 21 nephroblastomas investigated had statistically significantly decreased expression levels of miR-23a. A high level of HOXB4 mRNA was found in five out of 33 nephroblastomas including mixed, blastema-type and stroma-type tumors. Protein expression of HOXB4 was stronger in 15 out of 27 nephroblastomas of all subtypes in a semiquantitative comparison to normal kidney parenchyma. Our study demonstrates for the first time the regulation of HOXB4 by miR-23a. In comparison to mature kidney, nephroblastomas had low levels of miR-23a, and in a majority of them a stronger protein expression in comparison to mature kidney was found.

The pluripotent renal stem cell regulator SIX2 is activated in renal neoplasms and influences cellular proliferation and migration

Embryonal renal mesenchyme contains pluripotent progenitor cells characterized by expression of SIX2, which suppresses cellular differentiation. Additionally hypomethylation of the promotor region in renal neoplasms indicates a role of SIX2 in tumorigenesis. This study focuses therefore on the investigation of SIX2 in different renal neoplasms and the mode and consequences of SIX2 activation. Expression of SIX2 was determined in renal cell carcinomas, nephroblastomas, and dysplastic kidneys using immunohistochemistry and quantitative real-time polymerase chain reaction. Its potential mode of activation was assessed by measuring upstream activators by quantitative real-time polymerase chain reaction and the level of methylation of the promoter region by quantitative DNA methylation analysis. Consequences of SIX2 activation were investigated by overexpressing SIX2 in a cell line. Forty-seven of 49 renal clear cell carcinomas showed nuclear staining of SIX2, whereas all papillary carcinomas were negative. In nephroblastomas of various subtypes blastema showed a significant up-regulation (P < .01) and a strong nuclear protein expression of SIX2 in contrast to negative epithelial and mesenchymal areas. 11 cases of dysplastic kidneys were entirely negative. Upstream activators of SIX2 indicated an activation of the signal transduction pathway in most samples. No difference of promoter methylation status was observed between blastema and epithelial structures. A significantly higher percentage of cells in the S-phase and an increased migration were detected in the cell-line overexpressing SIX2. Our study suggests that activation of SIX2 might contribute to the pathogenesis of renal clear cell carcinomas and nephroblastomas. SIX2 also appears to be a valuable marker for minimal residual blastema contributing to the prognosis of nephroblastomas.

Gene expression analysis of blastemal component reveals genes associated with relapse mechanism in Wilms tumour

Wilms tumour (WT) is a paediatric kidney tumour, composed of blastemal, epithelial and stromal cells, with a relapse rate of approximately 15%. Long-term survival for patients with relapse remains approximately 50%. Current clinical and molecular research is directed towards identifying prognostic factors to define the minimal and intensive therapy for successful treatment of children with low and high risk of relapse, respectively. Blastemal component presents a high level of aggressiveness and responsiveness to chemotherapy. To identify molecular prognostic markers that are predictive of chemotherapy sensitivity in tumour relapse, blastemal-enriched samples from stage III and IV WT, from patients with relapse or without relapse, were analysed for 4608 human genes immobilised on a customised cDNA platform. These analyses revealed 69 differentially expressed genes, and the top nine genes were further evaluated by qRT-PCR in the initial WT samples. TSPAN3, NCOA6, CDO1, MPP2 and MCM2 were confirmed to be down-regulated in relapse WT, and TSPAN3 and NCOA6 were also validated in an independent sample group. Protein expression of MCM2 and NCOA6 were observed in 38% (13 out of 34) and 28% (9 out of 32), respectively, of independent stage III and IV WT blastema samples, without association with relapse. However, a significant association between MCM2 positive staining and chemotherapy as first treatment suggests the involvement of MCM2 with drug metabolism in WT blastemal cells.

Candidate genes and potential targets for therapeutics in Wilms' tumour

Wilms' tumour (WT) is the most common malignant renal tumour of childhood. During the past two decades or so, molecular studies carried out on biopsy specimens and tumour-derived cell lines have identified a multitude of chromosomal and epigenetic alterations in WT. In addition, a significant amount of evidence has been gathered to identify the genes and signalling pathways that play a defining role in its genesis, growth, survival and treatment responsiveness. As such, these molecules and mechanisms constitute potential targets for novel therapeutic strategies for refractory WT. In this report we aim to review some of the many candidate genes and intersecting pathways that underlie the complexities of WT biology.

Nephroblastoma with transcoelomic metastasis in a Japanese black bull

This paper describes a nephroblastoma with transcoelomic metastasis in a three-year-old Japanese black bull. At necropsy, a huge, oval neoplastic mass containing the residual right kidney was found. Moreover, severe transcoelomic metastasis occurred throughout the abdominal and thoracic cavities. Histologically, the mass was mainly composed of sheets, nests, islands and cords of polygonal blastemal cells with trabeculae of fibrous stroma. In some areas, epithelial elements composed of tubules and winding duct-like structures were also observed. Glomeruloid structures were scattered in these epithelial elements. Metastatic nodules were composed of blastemal and stromal elements, which were similar to those in the mass.

Genetic clonality is a feature unifying nephroblastomas regardless of the variety of morphological subtypes

Nephroblastomas are embryonal tumors exhibiting a wide variety of different morphological features and genetic changes. Some of the genetic aberrations were associated with a certain histological subtype. It is generally assumed that nephroblastomas develop as subclonal proliferations from nephrogenic rests. However, so far, a very limited amount of tumors from only part of the morphological spectrum of nephroblastomas was investigated. We therefore investigated the clonality of 45 tumors of all different histological subtypes. The number of each subtype was in accordance with the percentage of occurrence of the respective subtype. We analyzed a highly polymorphic locus of the human androgen receptor gene for nonrandom X-inactivation of genomic DNA using a methylation-sensitive restriction enzyme. Data were obtained for 39 tumors. Eighteen of the tumors included were noninformative in the genetic locus examined, the remaining 21 tumors were monoclonal regardless of the histological subtype. Our findings therefore support the hypothesis that Wilms' tumors are monoclonal proliferations despite their large variety of morphological features.

Histogenesis of human renal cell carcinoma by using electron microscopy and immunohistochemical techniques

Electron microscopy and immunohistochemical techniques are powerful tools for the determination of tissue origin. Both techniques have been used in the current experiment for histogenesis of renal cell carcinoma. Fifty kidney tumors were subjected to immunohistochemical detection for intermediate filaments cytokeratin and vimentin, which are normally expressed in epithelial tissue and mesenchymal tissues, respectively. Twenty cases of the above were examined by electron microscopy for detection of ultrastructure features. From each kidney, two specimens were taken, one from the diseased area and another far from it to serve as a control. Immunohistochemical study revealed in cases of renal cell carcinoma, cytokeratin and vimentin were expressed alone in 44% of cases, and 40% of cases, respectively. Twelve percent of cases were coexpressed with both cytokeratin and vimentin. Electron microscopic study of diseased specimens revealed the expression of desmosomes which was observed in almost all tumor specimens. The expression of the vimentin in some cases either alone or with cytokeratin was interpreted as a change in the characters of some tumor cells which indicates the need for additional techniques in such cases to get the proper interpretation. The prevalence of the expression of cytokeratin and the persistence existence of desmosomes indicate the epithelial origin of the tumor. This data is very beneficial for determination of line of therapy and follow up of the patients. The results confirm the power of combined use of both immunohistochemistry and electron microscopy in the field of histogenesis.

Imprinting, expression, and localisation of DLK1 in Wilms tumours

BACKGROUND

Loss of imprinting (LOI) of the H19/IGF2 domain is a common feature of Wilms tumour. The GTL2/DLK1 domain is also imprinted and is structurally similar to H19/IGF2. The question arises as to whether DLK1 also undergoes LOI in Wilms tumour, or whether the LOI mechanism is restricted to the H19/IGF2 domain.

AIM

To investigate the imprinting status of DLK1 in Wilms tumours with IGF2 LOI. The cellular localisation of DLK1 in the tumours was also examined.

METHODS

DLK1 expression was measured by quantitative real time polymerase chain reaction (Q-PCR) in 30 Wilms tumours that had previously been classified according to whether they had IGF2 LOI, WT1 mutations, or 11p15.5 loss of heterozygosity. Allele specific expression of DLK1 was examined by direct sequencing using a DLK1 exon 5 polymorphism (rs1802710). Immunohistochemical analysis of DLK1 was performed on 13 tumours and two intralobar nephrogenic rests, in addition to two fetal kidneys and one fetal skeletal muscle sample.

RESULTS

Ten of 30 tumours were heterozygous for rs1802710 and all tumours showed retention of imprinting of DLK1. Moderate to high expression of DLK1 was detected by Q-PCR in nine of 13 tumours with myogenic differentiation. Immunohistochemical expression of DLK1 was detected in the myogenic elements.

CONCLUSION

LOI does not occur at the GTL2/DLK1 domain in Wilms tumour. This finding suggests that LOI at 11p15.5 does not reflect non-specific disruption of a shared imprinting mechanism. DLK1 expression in Wilms tumour might reflect the presence of myogenic differentiation, rather than an alteration of its imprinting status.

Transcript profiling of Wilms tumors reveals connections to kidney morphogenesis and expression patterns associated with anaplasia

Anaplasia (unfavorable histology) is associated with therapy resistance and poor prognosis of Wilms tumor, but the molecular basis for this phenotype is unclear. Here, we used a cDNA array with 9240 clones relevant to cancer biology and/or kidney development to examine the expression profiles of 54 Wilms tumors, five normal kidneys and fetal kidney. By linking genes differentially expressed between fetal kidney and Wilms tumors to kidney morphogenesis, we found that genes expressed at a higher level in Wilms tumors tend to be expressed more in uninduced metanephrogenic mesenchyme or blastema than in their differentiated structures. Conversely, genes expressed at a lower level in Wilms tumors tend to be expressed less in uninduced metanephrogenic mesenchyme or blastema. We also identified 97 clones representing 76 Unigenes or unclustered ESTs that clearly separate anaplastic Wilms tumors from tumors with favorable histology. Genes in this set provide insight into the nature of the abnormal nuclear morphology of anaplastic tumors and may facilitate identification of molecular targets to improve their responsiveness to treatment.

Myogenesis in Wilms' tumors is associated with mutations of the WT1 gene and activation of Bcl-2 and the Wnt signaling pathway

Wilms tumors with WT1 mutations [ WT1(-)] have a stromal-predominant histology with varying extents of rhabdomyogenesis. These tumors also frequently have mutations in the beta-catenin gene ( CTNNB1). We have investigated the molecular events that may explain the origins of rhabdomyogenesis in WT1(-) tumors. Of 35 Wilms tumors, we identified 12 with WT1 mutations, of which 9 carried CTNNB1 mutations. We compared WT1 wild-type tumors [ WT1(+)] with WT1(-) tumors for histological features, localization of beta-catenin, Bcl-2 expression, and apoptosis using an in-situ end-labeling technique. WT1(+) tumors showed triphasic and blastemal- and epithelial predominant-histology. Expression of WT1, beta-catenin, and Bcl-2 recapitulated those of normal kidney epithelial development. Localization of beta-catenin was observed in the cytoplasm and cytoplasmic membrane of early glomerular epithelial structures. Bcl-2 is also expressed in condensing blastema and early glomerular epithelial structures which had little apoptosis. WT1(-) tumors, regardless of whether CTNNB1 mutations were detected or not, showed a stromal-rich phenotype with abundant expression of beta-catenin in the nucleus of the rhabdomyoblasts. Bcl-2 was expressed in rhabdomyoblasts, but not in blastemal cells undergoing apoptosis, suggesting that WT1 regulates Bcl-2 positively in the epithelial pathway, but negatively in the myogenic pathway. These data indicate that mutations in WT1 might alter the Wnt signaling pathway and Bcl-2 related-apoptosis. In WT1(-) tumors, the nuclear accumulation of beta-catenin and Bcl-2 expression are associated with rhabdomyogenesis, and dysregulation of Bcl-2 may be a mechanism by which the histogenesis (loss of blastemal component, muscle differentiation) may be explained.

MIB-1 (KI-67) Proliferation Index and Cyclin-Dependent Kinase Inhibitor p27Kip1 Protein Expression in Nephroblastoma

PURPOSE

A number of studies have indicated that the tumor proliferation marker MIB-1 and cell cycle inhibitor p27(Kip1) expression are of prognostic importance in a variety of cancers. The present study was performed to evaluate the prognostic value of these molecules in Wilms' tumors.

EXPERIMENTAL DESIGN

MIB-1 and p27(Kip1) expressions were investigated by the means of immunohistochemical analysis of 62 Wilms' tumor. Patients were preoperatively treated by chemotherapeutic agents and had a mean follow-up of 5.7 years.

RESULTS

MIB-1 and p27(Kip1) were expressed in normal kidney tissues and in the three main components of Wilms' tumor, i.e., the blastemal, epithelial, and stromal cells. In Wilms' tumors, the percentage of MIB-1-positive cells in the blastema ranged between 0 and 42% (mean, 9.4%) and in the epithelial component between 0 and 53% (mean, 19.9%), with a significant difference (P < 0.01). The percentage of blastemal p27(Kip1)-positive cells ranged between 3 and 85% (mean, 55.1%) and for the epithelial component between 1 and 87% (mean, 59%). There was a significant inverse relationship between blastemal MIB-1 and p27(Kip1) expression in Wilms' tumor. Univariate analysis showed that blastemal MIB-1 and p27(Kip1) expression were indicative for clinical progression and tumor-specific survival. In a multivariate analysis, blastemal MIB-1 and p27(Kip1) protein expression proved to be an independent prognostic for clinical progression besides stage.

CONCLUSIONS

It was concluded that both MIB-1-based proliferative activity and p27(Kip1) protein expression in the blastema have prognostic impact in Wilms' tumor.

Comparative immunohistochemical analysis of developing kidneys, nephroblastomas and related tumors: considerations on their histogenesis

Immunoperoxidase analysis was performed to evaluate the phenotypic expression of eight renal differentiation antigens in five nephroblastomas, one clear cell sarcoma of the kidney (CCSK), one rhabdoid tumor of the kidney (RTK), and four related tumors. A total of 19 fetal and pediatric kidneys, including two 6th-week mesonephric tissues, were comparatively studied. All the specimens were fixed in formalin and embedded in paraffin. Neural cell adhesion molecule (NCAM), a marker of the nephrogenic zone of the developing kidney, was consistently expressed in the epithelial and blastematous components of nephroblastomas of the common type. The epithelial components also commonly expressed NK1 and Leu 7 (CD57), and the findings may reflect that both were positive in immature proximal tubules directly differentiating from the NCAM-positive immature fetal tubuloglomerular buds. In two cases, the epithelial component was immunoreactive for CD10 and WT1 gene product (WT1-GP). Leu M1, epithelial membrane antigen and CA15-3 were only focally expressed in nephroblastomas. Rhabdomyoblasts in the stroma were positive for WT1-GP. CCSK was featured by the expression of NCAM and CD10. In RTK, focal epithelial differentiation was discerned, with focal positivity of WT1-GP and negativity of NCAM. In congenital mesoblastic nephroma, the stromal spindle cells were strongly immunoreactive for WT1-GP, while WT1-GP was not expressed in solitary multilocular cyst of the kidney. Pancortical nephroblastomatosis was featured by the diffuse subcapsular reappearance of immature metanephric tissue. Nephroblastomas and related conditions thus offer an adequate model for studying human nephrogenesis.

Cystic partially differentiated nephroblastoma in an adult: an immunohistochemical, lectin histochemical and ultrastructural study

AIMS

Cystic partially differentiated nephroblastoma (CPDN) is an uncommon renal multicystic tumour, usually affecting early infants. To our knowledge, this report describes the first case of CPDN occurring in an adult.

METHODS AND RESULTS

A 45-year-old man was found incidentally to have a left renal cystic tumour, measuring 20 mm in diameter, at the lower pole far from the pelvis. The tumour was composed of multilocular cystic spaces of variable size and intervening septa without solid nodular areas. The cysts were lined by a single layer of flattened, hobnail, or columnar epithelium. The septa were made of mesenchymal cells, which were admixed with small numbers of loosely aggregated blastemal cells, occasional tubular structures in various stages of development, and a few glomeruloid structures. The tumour cells had no anaplasia, and mitoses were rare. Immunohistochemical and lectin histochemical studies revealed that the cyst lining epithelium and the tubular structures in the septa expressed predominantly the markers for distal tubules and collecting ducts. Ultrastructurally, the cyst lining cells closely resembled collecting duct cells while some tubular structures showed an immature nephrogenic morphology. The patient was alive and well without evidence of recurrence 11 months after surgery.

CONCLUSIONS

CPDN does occur in adults, as experienced in Wilms' tumour, though its incidence is extremely low. This study suggests that CPDN may show maturation intermediate between cystic nephroma and Wilms' tumour, even in adult cases.

Cystic embryonal sarcoma of kidney: a case report

BACKGROUND

Morphologic analysis of malignant renal tumors of childhood and adolescence has resulted in the identification of a variety of tumor types with characteristic histology and clinical behavior. The authors report a case of renal sarcoma in a 19-year-old male that differs in morphology from the various established categories of primitive renal tumors.

METHODS

Sections taken from the nephrectomy specimen were stained by routine methods and by immunohistochemistry for stromal and epithelial markers, and for proliferation markers. In addition, ultrastructural studies were undertaken.

RESULTS

The tumor, which the authors termed cystic embryonal sarcoma, was comprised of poorly differentiated malignant mesenchyme in a myxoid stroma. Numerous epithelial-lined cysts were present. The distribution of the cysts and proliferation kinetics of cyst-lining epithelial cells suggested that they were derived from entrapped renal tubules. The tumor showed early recurrence postoperatively and after aggressive chemotherapy. The pathologic features and clinical behavior of the tumor resemble those of 2 previously reported cases and an additional 25 cases from the files of the National Wilms' Tumor Study Pathology Center.

CONCLUSIONS

The clinical and histologic features of cystic embryonal sarcoma differ from those of other renal tumors of childhood and adolescence, and the tumor appears to be a novel form of renal malignancy.

Correlation of germ-line mutations and two-hit inactivation of the WT1 gene with Wilms tumors of stromal-predominant histology

The WT1 gene, located on chromosome 11p13, is mutated in a low number of Wilms tumors (WTs). Germ-line mutations in the WT1 gene are found in patients with bilateral WT and/or associated genital tract malformations (GU). We have identified 19 hemizygous WT1 gene mutations/deletions in 64 patient samples. The histology of the tumors with mutations was stromal-predominant in 13, triphasic in 3, blastemal-predominant in 1, and unknown in 2 cases. Thirteen of 21 patients with stromal-predominant tumors had WT1 mutations and 10 of these were present in the germ line. Of the patients with germ-line alterations, six had GU and a unilateral tumor, two had a bilateral tumor and normal GU tracts, and two had a unilateral tumor and normal GU. Three mutations were tumor-specific and were found in patients with unilateral tumors without GU. These data demonstrate a correlation of WT1 mutations with stromal-predominant histology, suggesting that a germ-line mutation in WT1 predisposes to the development of tumors with this histology. Twelve mutations are nonsense mutations resulting in truncations at different positions in the WT1 protein and only two are missense mutations. Of the stromal-predominant tumors, 67% showed loss of heterozygosity, and in one tumor a different somatic mutation in addition to the germ-line mutation was identified. These data show that in a large proportion of a histopathologically distinct subset of WTs the classical two-hit inactivation model, with loss of a functional WT1 protein, is the underlying cause of tumor development.

Ultrastructure of cellular congenital mesoblastic nephroma

A detailed ultrastructural description of the cellular variant of congenital mesoblastic nephroma (CMN) is presented and compared to the classical form. Studied were 9 cases of the cellular variant, 6 mixed (cellular/classical) tumors, and 1 classical CMN. The occurrence of a broad selection of ultrastructural features was assessed using a semiquantitative scoring system. The results indicate that cellular CMNs are composed mainly of primitive mesenchymal cells, but also usually contain varying numbers of differentiating fibroblasts and myofibroblasts. This entity thus bears a closer resemblance at the ultrastructural level of organization to infantile fibrosarcoma than to conventional fibrosarcoma. Electron microscopy can be useful in distinguishing this relatively benign entity from the several malignancies with which it is sometimes confused.

Role of immunocytochemistry, electron microscopy, and DNA analysis in fine-needle aspiration biopsy diagnosis of Wilms' tumor

We reviewed the cytologic features and results of ancillary studies in eight fine-needle aspiration biopsies (FNAB) performed by posterior approach in 8 patients with unresectable Wilms' tumor (WT). Chemotherapy was given following the FNAB diagnosis of WT, which was confirmed subsequently by histologic examination of surgically resected specimens. Indications for FNAB included: unresectable tumor, bilateral disease, initial presentation with metastatic disease, uncertainty regarding tumor site, and documentation of recurrence. Cytologic examination revealed blastemal cells (8/8 aspirates), spindle cells (3/8 aspirates), and epithelial differentiation or tubules (3/8 aspirates). There was no cytologic evidence of anaplasia in any of the cases. Immunocytochemical studies on cell blocks and/or smears showed cytokeratin positivity in 5/8 and vimentin positivity in 5/5 of the aspirates in which these studies were performed. Focal positivity for neuron-specific enolase (NSE) was seen in 3/3 aspirates. Stains for actin and leukocyte-common antigen were negative (0/3 and 0/2 aspirates, respectively). DNA ploidy analysis of the aspiration material by flow cytometry revealed near-diploid populations in three aspirates. Electron microscopic findings helpful for diagnosis included: cell junctions, microvilli, flocculent basement membrane-like material, cilia, autophagolysosomes, and lack of neuroectodermal differentiation. Diagnostic morphologic pitfalls for an incorrect diagnosis of neuroblastoma included nuclear molding (all aspirates), pseudorosette formation (one aspirate), and focal NSE positivity (3/3 aspirates). None of the tumors showed anaplasia on histologic examination. Cytologic recognition of the triphasic cellular components of WT (blastemal cells, spindle cells, and epithelial cells) can be helpful for a correct diagnosis; however, in 5/8 aspirates in this study, only the blastemal component was present. In these cases, immunocytochemical stains and electron microscopy proved useful in arriving at a correct FNAB diagnosis of WT. However, NSE positivity can be a pitfall for a diagnosis of neuroblastoma if the radiologic, clinical, and other cytologic features are not clearly delineated. Presence of cytokeratin and vimentin positivity would be helpful in the diagnosis of WT in such instances.

Extrarenal Wilms' tumor: an ultrastructural and immunoelectron microscopic case report

Wilms' tumor is the most common malignancy of the genitourinary tract in children but the occurrence of extrarenal Wilms' tumor is extremely rare. Extrarenal Wilms' tumor, which by definition excludes a primary tumor in the kidney, has been reported less than fifty times. The ultrastructural appearance of renal Wilms' tumor has been well documented, but the present report is believed to be the first description of the ultrastructural appearance of extrarenal Wilms' tumor. The authors report, for the first time, localization of intermediate filament proteins (vimentin and cytokeratin) and epithelial membrane antigen (EMA) by immunoelectron microscopy in this neoplasm. Demonstration of the coexpression of vimentin and cytokeratin within the same blastemal cell, as well as the identification of desmosomes in a cell with vimentin intermediate filaments, suggests a relationship between stroma, blastema, and epithelia similar to that proposed in renal Wilms' tumor.

The value of ultrastructural evaluation in the diagnosis of renal tumors: a general overview

The understanding of renal neoplasia has advanced significantly in the last 20 years. New challenges have arisen as a consequence of prolonged dialysis and renal transplantation becoming the therapeutic modes to deal with chronic renal disease. Immunosuppression resulting from primary disease processes or as a result of clinical intervention has resulted in an increase in neoplasia in general and changes in manifestations and clinical behavior of tumors. Special techniques such as immunocytochemistry and electron microscopy have provided information that has resulted in refinement of diagnostic and conceptual issues. The variable gross and histological manifestation of many of the renal neoplasms can be explained at least in part by reflecting on the new fundamental knowledge that has been acquired regarding renal developmental biology. A more aggressive approach from a therapeutic point of view placing emphasis on specific treatment protocols for the various nosologic entities further emphasizes the need to understand the advances that have taken place in the field. This article provides an overview of the subject, with emphasis on an overall conceptual understanding, to serve as a practical framework. The articles that follow address the specific current role of ultrastructure in the diagnosis and understanding of renal neoplasms.

Secretion of gastrin-releasing peptide by retroperitoneal tumors

PURPOSE

Gastrin-releasing peptide (GRP) is a neuropeptide with growth factor activity in vitro for a variety of tumors including neuroblastoma. If GRP is secreted by neuroblastomas, its detection in serum might be an excellent way to both diagnose and monitor this tumor in patients.

METHODS

Small portions of resected tumor specimens were maintained in tissue culture as tumor explants for 24 hours. The tumors included: 3 ganglioneuromas, 1 neuroblastoma, 1 primitive neuroectodermal tumor, 1 Wilms' tumor, 1 rhabdoid tumor, and 1 benign brachial plexus tumor. Control flasks were maintained simultaneously under identical conditions. After 24 hours of incubation, the tumor-conditioned media and the control media were assayed in duplicate for [GRP] using a radioimmunoassay.

RESULTS

All the conditioned media from the benign tumors contained < 25 pg/mL net GRP, whereas all the malignant tumor-conditioned media contained > or = 45 pg/mL (P = 0.003).

CONCLUSIONS

These data suggest that GRP is secreted by pediatric retroperitoneal tumors and that the amount secreted varies directly with the degree of malignancy of the tumor. This study suggests that GRP may be a candidate tumor marker for pediatric retroperitoneal tumors.

Bone metastasizing renal tumor of childhood. A clinicopathological study of eleven cases from the Prague Pediatric Tumor Registry

Eleven patients with bone metastasizing renal tumor of childhood (BMRTCh) who were diagnosed and treated in our departments over a 20-year period were reviewed. The incidence among all malignant renal tumors in children up to 15 years of age in our files was 3.7%. The male to female ratio was 10:1. The morphology had a uniform, predominantly clear cell finely vascularized pattern in all of them. Various previously recognized variations of the classic pattern such as hyalinization, nuclear palisading and cyst formation were observed in some patients. Electron microscopy showed that coarse vacuolization of the tumor seen at the light microscopic level was due to distended extracellular spaces surrounded by tumor cells and their cytoplasmic processes. Immunohistochemistry of the tumor cells revealed positive vimentin in all cases, and focally positive muscle specific actin in one. A prominent feature was fascicles of perivascular spindle cells. They were considered to be tumor cells rather than stromal elements since their morphology was close to the appearance of the polygonal tumor cells. The follow up data were available for ten patients. Four developed bone metastases, three of them died of the disease progression. Another patient died of lymph node dissemination and gastrointestinal bleeding. Six patients survived for a period of 29 months to 14 years following the diagnosis.

Characterization of a monoclonal antibody recognizing selective epithelial elements of Wilms' tumors and fetal kidneys

A new antigen was detected using a monoclonal antibody generated against malignant blastema from a Wilms' tumor. This antigen showed variable expression in malignant blastemal cells but was never detected in normal blastema of fetal kidneys irrespective of gestational stage. In a series of 16 Wilms' tumors, the most intense and consistent staining was seen in tubule-associated epithelial cells. Such tubular staining is not surprising as the putative induction of malignant blastema to differentiate into malignant tubules is thought to parallel normal tubulogenesis. This antigen was also associated with epithelial cells located in a variety of fetal kidney structures. Again, the staining was most consistent in tubular epithelia. This monoclonal antibody reactive with a blastemal-epithelial-tubular (BET) antigen should be of value in studying the induction of epithelial differentiation in the normal and diseased human kidney.

Characterization of a monoclonal antibody recognizing the blastemal element of Wilms' tumors and fetal kidneys

A blastema-associated antigen (BLA-1) was detected using a monoclonal antibody against malignant blastema from a Wilms' tumor. The localization of BLA-1 was investigated in a series of nine Wilms' cases, five fetal, one childhood, and two adult kidneys. In this series, BLA-1 antibody consistently stained cell surfaces of all Wilms' tumors containing blastemal components. The same staining pattern was maintained in tumors grown as heterotransplants in nude mice. The expression of BLA-1 antigen was examined in normal blastema of fetal kidneys. BLA-1 was immunolocalized to condensed blastemal cells in the nephrogenic zone throughout gestation. In addition, kidney samples from a young child or adults contained no blastemal cells and therefore showed no blastemal cell surface staining. Glomerular mesangial cell staining was demonstrated in kidneys from 12 weeks of gestation through adulthood. This staining in developing and mature glomeruli implies that mesangial cells may be derived from condensed blastemal cells. The finding of a cell surface antigen common to Wilms' blastema, fetal blastema, and mesangial cells has not been previously demonstrated.

Serum-free culture and characterization of renal epithelial cells isolated from human fetal kidneys of varying gestational age

Cell cultures were initiated from seven human fetal kidneys that varied in gestational age from 90 days to newborn. The growth medium utilized was a 1:1 mixture of Dulbecco's modified Eagle's and Ham's F12 supplemented with selenium (5 ng/ml), insulin (5 micrograms/ml), transferrin (5 micrograms/ml), hydrocortisone (36 ng/ml), triiodothyronine (4 pg/ml), and epidermal growth factor (10 ng/ml). For all the kidney isolates, initial cell attachment occurred within 12 h through multicell spheroids, and by 24 h a rapidly growing population of cells was obtained. Confluency was reached within 3 to 6 days. A combination of light microscopy, immunohistochemistry, and ultrastructural evaluation was utilized to characterize the resulting cultures as epithelial and homogeneous within each isolate and among the isolates. That is, regardless of gestational age of the fetal kidney used as starting material, an identical or highly similar population of cells was obtained. By light microscopy, the cultures were noted to form very few domes, the number being an indication of transport activity. However, ultrastructural examination revealed that the cells were noted to form domes composed of only a few cells or "micro-domes" that would not be visible by light microscopy. Within the micro-domes as well as other areas of the monolayer an apparent absence of tight junctions was noted by routine transmission electron microscopy. However, by freeze fracture analysis cells were shown to possess sealing strands, the structural component of tight junctions. It is postulated that the tight junctions of fetal epithelial cells are structurally altered as compared to tight junctions in adult renal epithelial cell cultures.

Malignant rhabdoid tumor of the kidney expresses insulin-like growth factor II transcripts

Insulin-like growth factor II (IGF-II) is thought to play a major role in fetal growth and development. High levels have been demonstrated in blastemal cells of both normal fetal kidney and Wilms' Tumor (WT). In this report, 2 cases of malignant rhabdoid tumor of the kidney (MRTK) were studied to detect the expression of IGF-II mRNA by in situ hybridization using 35S labelled RNA riboprobes. Results showed highly strong and specific IGF-II mRNA expression by tumor cells.

Spectrum of differentiation in pediatric epithelial tumors of kidney: report of two cases

Two unusual presentations of childhood renal cell epithelial tumors including one whose unique clinical manifestation was polycythemia are described. One was a renal cell carcinoma which was so poorly differentiated that ancillary histopathologic techniques were necessary to arrive at the correct diagnosis. The other case represented the opposite extreme being so well-differentiated as to raise the differential diagnosis of renal cell carcinoma versus renal cell adenoma with blastemal areas. These case studies exemplify the practical role for specialized histopathologic techniques in diagnosing pediatric renal tumors, which may not be feasibly or even accurately categorized into known renal tumor types using routine diagnostic methods.

An immunohistochemical study comparing clear cell sarcoma of the kidney and Wilms' tumor

This study explores immunohistochemical characteristics that may be of diagnostic value in differentiating clear cell sarcoma of the kidney (CCSK) from Wilms' tumor (WT) and may provide some insight into the histogenesis of CCSK. Formalin-fixed, paraffin-embedded sections of 8 CCSK and 9 WT were stained, using the standard avidin-biotin peroxidase complex method, for vimentin (VIM), Factor-8 related antigen (F8A), epithelial membrane antigen (EMA), desmin (DES), S-100 protein and Mac 387. CCSK cells consistently exhibited moderate to strong diffuse cytoplasmic positivity for VIM and were negative for F8A, EMA, DES, S-100 and Mac 387. In contrast, only patchy groups of stromal cells and primitive glomeruloid structures in WT exhibited VIM-positivity. Blastemal cells were VIM-negative. Stromal cells with rhabdomyomatous differentiation exhibited cytoplasmic positivity for DES. Epithelial cells of maturing tubular structures showed EMA-positivity whereas immature tubular structures were EMA-negative. Neither blastemal, stromal nor epithelial elements in WT were positive for F8A, S-100 or Mac 387. Podocytes and mesangial cells of glomeruli in 3 mid-trimester human abortuses (controls) exhibited moderate to strong VIM-positivity. The importance of differentiating CCSK from WT has been repeatedly emphasized because of its poorer prognosis and the necessity of adding Adriamycin to the chemotherapeutic regime. The consistent VIM-positivity of CCSK cells can be a useful feature in differentiating it from "blastemal-predominant" WT, with which it is often confused. Although vimentin expression by CCSK cells is consistent with a mesenchymal character, the possibility of a histogenetic link with glomerular podocytes or mesangial cells should also be considered.

Clear cell sarcoma of kidney. Two cases in adults

BACKGROUND

Clear cell sarcoma of kidney (CCSK) is an aggressive renal tumor occurring most frequently in the second and third years of life. Although it has been reported in the literature in patients as old as 21 years of age, there has been no report focusing on adults with CCSK. The authors describe two cases of CCSK in men and the findings at autopsy.

METHODS AND RESULTS

Histologically, the renal tumors consisted of a homogeneous proliferation of polygonal or short spindle cells with faintly eosinophilic cytoplasm supported by a network of small vessels. Ultrastructurally, clusters of tumor cells were surrounded by collagen bundles. Elongated cytoplasmic processes, dilated rough endoplasmic reticulum, and intermediate filaments in the cytoplasm; primitive desmosome-like junctional structures; and incomplete basal lamina were observed. Immunohistochemically, tumor cells had positive results only for vimentin. Cytokeratins, epithelial membrane antigen, desmin, myoglobin, S-100 protein, neuron-specific enolase, and chromogranin A were not detected in the tumor cells. Both patients died within 2 years of onset of disease, and autopsy showed widespread metastases, especially in the soft tissue and bone.

CONCLUSIONS

Morphologic findings and an aggressive clinical course with metastasis to the bone and soft tissue are supportive of the diagnosis of CCSK in these patients.

Congenital mesoblastic nephroma: an immunohistochemical and lectin study

Eight cases of congenital mesoblastic nephroma (CMN) were examined. Three CMNs were of the classical (typical) variant, two were cellular (atypical), and three showed a mixed pattern. A panel of nephron segment-specific tubular epithelial markers (the lectins Tetragonolobus purpureas, Phaseolus vulgaris erythroagglutinin, and Arachis hypogaea and antibodies to epithelial membrane antigen, cytokeratin, and Tamm-Horsfall protein) were used to differentiate epithelial structures within the tumor. Antibodies against vimentin, desmin, and muscle-specific actin were used as mesenchymal markers. A monoclonal antibody to the long (embryonic) form of polysialic acid (PSA) on the neural cell adhesion molecule was used as a putative renal oncodevelopmental marker. An antibody to proliferating cell nuclear antigen also was applied, which revealed increased proliferative rate in cellular CMNs. In addition to clearly entrapped native renal tubules, CMNs contain tubular structures with immature, dysplastic epithelium and occasional epithelial cell clusters embedded deep within the tumor. These immature tubules and clusters express distal nephron, including collecting duct markers and, occasionally, vimentin and PSA. We propose that these primitive tubules and epithelial structures may originate from the ureteric bud. An epithelial differentiation of the tumor cells also is possible. In one pure cellular CMN and two mixed CMNs the cellular component showed diffuse staining for PSA. The PSA (neural cell adhesion molecule) expression of the cellular component suggests that CMN may originate from the uninduced nephrogenic mesenchyme.

Unresectable stage IV nephroblastoma: a potential indication for fine-needle aspiration biopsy in children

In the United States, the initial morphologic diagnosis of nephroblastoma is usually determined on a nephrectomy specimen prior to the initiation of any additional therapy. Such an approach, however, is not appropriate in all children; we believe that fine-needle aspiration biopsies (FNAB) should be the initial diagnostic procedure in a minority of patients with suspected Wilms' tumor. One such group of patients is those who present with stage IV disease, especially when it is considered unresectable. Herein we present two children with advanced Wilms' tumor to support our contention. The initial microscopic diagnosis in each was made by FNAB. Following chemotherapy, predominantly necrotic Wilms' tumors were excised. Both patients are alive with no evidence of residual disease or untoward affects from the aspiration procedure.

Mesoblastic nephroma metastatic to the lungs and heart--another face of this peculiar lesion: case report and review of the literature

A case of mesoblastic nephroma in a 14-month-old girl who developed consecutive metastases in the lung and the heart is presented. This tumor is considered to be benign and cured by surgery only. Recurrent cases are extremely rare and usually related to unclear surgical margins. Metastatic mesoblastic nephroma has been previously described in only two cases. The present case highlights a new, previously undescribed feature--the ability to metastasize to sites other than lung.

Developmental pattern of Thy-1 immunoreactivity in the human kidney and the application to pediatric renal neoplasms

The localization of Thy-1, a surface membrane lipoglycoprotein, was investigated using a monoclonal antibody specific for human Thy-1 (HB-2S-1). The localization of Thy-1 during development was established in a series of five fetal, three childhood, and two adult normal kidneys. In this series, Thy-1 immunolocalization progressed from mesangial and endothelial cell staining in the 16- to 17-week fetuses to similar staining along with staining of the parietal epithelium of the capsule and proximal tubule staining in the 20- to 24-week fetuses. Glomerular mesangial cell and endothelial cell staining was absent by 9 months postnatally when the adult pattern of staining was apparent. The localization of Thy-1 during development was also compared with a series of pediatric renal tumors including 14 Wilms' tumors, 3 congenital mesoblastic nephromas, 1 clear cell sarcoma, and 1 pediatric renal cell carcinoma. Thy-1 staining was demonstrated in epithelial tubules of Wilms' tumors and in the spindle-shaped cells of congenital mesoblastic nephroma correlating with Thy-1 immunoreactivity in the kidney proximal tubule and fetal medullary stroma, respectively. Thy-1 staining was absent in the anaplastic epithelial Wilms' tumor, the renal cell carcinoma, and the clear cell sarcoma. This staining pattern fails to provide evidence that these tumors may arise from the medullary mesenchyme or the differentiated proximal convoluted tubule. These results show that Thy-1 is a renal differentiation marker and is useful in the characterization of tumors of renal development.

The expression of the Wilms' tumour gene, WT1, in the developing mammalian embryo

In the developing mouse, the Wilms' tumour gene, WT1, is first expressed in the intermediate mesenchyme lateral to the coelomic cavity (13 somite, early 9 dpc embryo). A few hours later, it is present around all the cavity and in the urogenital ridge (the earliest mesonephric tubules) and the differentiating heart mesothelium. By 11 dpc, expression is in the uninduced metanephric mesenchyme and in the presumptive motor neurons of the spinal cord. By 12.5 dpc, WT1 expression has increased in the induced mesenchyme of the kidney and a day later is particularly marked in the nephrogenic condensations. At 13.5 dpc, WT1 is briefly expressed in some differentiating body-wall musculature, while two days later, there is a small domain of expression in the roof of the fourth ventricle of the brain. By day 20, however, expression has become restricted to the kidney glomeruli. RNA-PCR analysis on 12.5 dpc embryos and on adult tissues shows that WT1 is weakly expressed in both eye and tongue. The expression pattern in human embryos (28-70 days) is very similar to that in the equivalent mouse stages (10-15 dpc). The results indicate that WT1 is mainly present in mesodermally derived tissues, although exceptions are ectodermally derived spinal cord and brain. The data indicate that WT1 plays a role in mediating some cases of the mesenchyme-to-epithelial transition, but its expression elsewhere argues that it has other tissue-specific roles in development.

PAX8, a human paired box gene: isolation and expression in developing thyroid, kidney and Wilms’ tumors

Recent evidence indicates a crucial role for paired box genes in mouse and human embryogenesis. The murine Pax8 gene encodes a sequence-specific transcription factor and is expressed in the developing secretory system as well as in the developing and adult thyroid. This restricted expression pattern suggested involvement of the Pax8 gene in the morphogenesis of the above organs and prompted us to investigate the PAX8 gene in humans. In this report, we describe the isolation and characterization of PAX8 cDNAs from a human adult kidney cDNA library. An open reading frame of 450 amino acids contains the 128 amino acid paired domain at its amino-terminal end. The predicted human and mouse Pax8 proteins show 97.8% conservation and are identical in their paired domains. Two independent cDNA clones reveal differential splicing of the PAX8 transcripts resulting in the removal of a 63 amino acid serine-rich region from the carboxy end of the predicted Pax8 protein. The truncated Pax8 protein becomes more similar to the predicted murine Pax2 protein, that is also expressed during kidney development and lacks the serine rich region. RNAse protection analysis shows the presence of both PAX8 transcripts in human thyroid, kidney and five Wilms’ tumors. No truncated Pax8 transcripts could be detected in mouse kidney. In situ hybridization to sections of human embryonic and fetal kidney showed expression of PAX8 in condensed mesenchyme, comma-shaped and S-shaped bodies. In contrast, PAX2 expression was present mainly in the very early stages of differentiation, in the induced, condensing mesenchyme. This restricted expression pattern suggests a specific role for both genes during glomeruli maturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumour suppression associated with expression of human insulin-like growth factor II

Recent circumstantial evidence has implicated Insulin-like growth factor II in the genesis of several tumour types, notably developmental tumours (Scott et al., 1985; Schofield & Tate, 1987; Wilkins et al., 1989). This type of tumour, thought to originate during the defective differentiation of organ precursors (Miereau et al., 1987), often expresses greatly elevated levels of mRNA for IGF-II, a known mitogen for these cells and abundantly expressed in their presumed normal counterparts (Scott et al., 1985; Schofield & Tate, 1987; Gray et al., 1987). It has been proposed that continued, inappropriate expression of this gene drives tumour growth by an autocrine mechanism. In order to examine the potential role of IGF-II in the growth of tumour cells an IGF-II cDNA was introduced into a retroviral expression vector, and used to infect a cloned fibroblast cell line. Expression of IGF-II conferred a degree of serum independence of growth in cell culture, however, when cells were injected into nude mice as subcutaneous grafts, clones expressing IGF-II from the retrovirus were found to have a greatly increased (five fold) latency of sarcoma formation. After a prolonged lag all cell lines eventually gave rise to tumours in which the introduced IGF-II genes had either been lost or inactivated, suggesting that in this system IGF-II acts as a tumour suppressor gene.

Wilms' tumour associated with deep cystic nephroma-like changes: three cases of a putative Wilms' tumour precursor

We describe three cases of Wilms' tumour accompanied by central pericalyceal multicystic lesions closely resembling those seen in cystic nephroma. In continuity with these lesions or elsewhere in the kidney were areas of dysplastic renal tissue of the type sometimes referred to as intralobar nephroblastomatosis. A close homology of tissue differentiation was observed between the dysplastic lesions and the interstitial components of the cystic lesions. These findings support the hypothesis that, in some cases at least, cystic nephroma has more in common with the group of dysplastic lesions referred to as the nephroblastomatosis complex than with the true renal tumours of childhood.

Renal cell carcinoma in children: histology, immunohistochemistry, and follow-up of 10 cases

Ten renal cell carcinomas in children under 15 years were investigated. The average age was 122.5 months and the girls predominated in our cases (7 girls, 3 boys). By using the classification of Thoenes et al., Pathol Res Pract 181: 125-143, 1986 a predominance of clear cell-eosinophilic tumor cell type and of the tubulopapillary growth pattern was found. Immunohistochemistry revealed a heterogeneity of cytokeratin expression. By using the monoclonal antibodies Cam 5.2 and KL 1, cytokeratins were found in 7 cases each. The other 4 cytokeratin antibodies used were less sensitive. The expression of cytokeratin 13 in 3 cases suggested a more complex histogenesis than assumed. Vimentin was found in 3 tumors, but an association to a higher grade (G) of malignancy was not found in these cases. One tumor expressed the Tamm-Horsfall-protein, which is predominantly found in the distal tubule of the normal kidney. In summary the results of immunohistochemistry characterized the great heterogeneity of these tumors. Follow-up information was available in 9 cases. All patients with G I- and G II-tumors were free of disease after an average time of 39.6 months (mean 27 months). Two of the 3 cases with G III-tumors died after 9 and 15 months, despite additional chemo- or radiotherapy. Therefore tumors of grade I and II of the Thoenes classification seem to have a good prognosis.

Pathologic delineation of the papillonodular type of cystic partially differentiated nephroblastoma. A review of 11 cases

Eleven cases of a previously unrecognized papillonodular variant of cystic partially differentiated nephroblastoma (CPDN) are described. This type of CPDN has all the features of the conventional type of CPDN; however, in addition, there are grossly demonstrable papillonodular projections extending from the septa into the cyst lumina. The septa do not show any expansile tumor masses. Like most cases of the conventional type, this new type of CPDN was usually diagnosed in infants. Nephrectomy (total in 10 and partial in 1) was done in these cases. Additional chemotherapy with or without radiation therapy was given in seven cases. No recurrence was noted during the period extending from 21 months to 8 years in the eight cases in which follow-up data are available. Nephrectomy with regular follow-up visits for possible recurrence may be the management of choice. Pathologists should be aware of this variant of CPDN so that overtreatment can be avoided. The revised criteria for CPDN can be summarized as follows: (1) The discrete entirely cystic tumor contains luminal papillonodules in some cases. (2) Septa and the papillonodules, when present, are the only solid portion of the tumor and contain blastemal cells admixed with their normal and aberrant derivatives. (3) The tumor without and with papillonodules is classified as a conventional and papillonodular type of CPDN, respectively.

Somatic cell hybrid and long-range physical mapping of 11p13 microdissected genomic clones

Microdissection and microcloning of banded human metaphase chromosomes have been used to construct a genomic library of 20,000 clones that is highly enriched for chromosome 11p13 DNA sequences. Clones from this library have been mapped on a panel of human-rodent somatic cell hybrids that divides the region from distal p12 to proximal p14 into seven physical intervals, A total of 1500 clones has been isolated, 250 clones have been characterized, and 58 clones have been mapped. Six of the clones were used to complete a long-range physical map of 7.5 megabases through the region. Two of the clones are localized to the Wilms tumor (WT) region, three are localized to the aniridia (AN2) region, and two are localized to the region between WT and AN2. The library represents DNA sequences spanning a distance of approximately 13 x 10(6) base pairs, with an average density of one clone per 37,000 base pairs.

Panlobar nephroblastomatosis: a distinctive form of renal dysplasia associated with Wilms' tumour

An increasing variety of dysplastic lesions of metanephric origin ('the nephroblastomatosis complex') have been recognized as precursors of Wilms' tumour. We describe here four cases of a hitherto unrecognized renal dysplasia associated with Wilms' tumour and having a panlobar distribution. It has many features in common with the intralobar form of nephroblastomatosis, but differs in extending through the full thickness of the renal substance from calyx to capsule. These cases are also characterized by an increased proportion of well-differentiated tissue elements and by the presence, in some cases, of anomalous metanephric differentiation in the pericalyceal tissues or renal capsule. The presence of Wilms' tissue arising deep in the renal substance should alert the pathologist to make a thorough search for associated dysplastic elements in the kidney.

Glutathione S-transferase expression in fetal kidney and Wilms' tumour

The glutathione S-transferases (GSTs) have been implicated in carcinogenesis and tumour drug-therapy resistance. In this study GST pi was the predominant isoenzyme in the fetal human kidney. It was present in differentiated epithelial structures but never in the primitive mesenchyme. By contrast most cases of Wilms' tumours showed GST pi in both epithelial structures and undifferentiated blastema. The level of expression, as assessed by immunostaining, was no more than moderate, and was generally higher in differentiated elements. In only one case was GST alpha found in Wilms' tumour. This study had demonstrated a difference between fetal kidney and Wilms' tumour blastema in terms of GST expression.